Electrode lead-in for metal vacuum vessels



Aug. 10, w DALLENBACH ELECTRODE LEAD-IN FOR METAL VACUUM VESSELS FiledOct. 25, 1934 \NVENTOR 6Pcer DHenbach ATTORNEYS Patented Aug. 19 37ELECTRODE LEAD-IN FOR METAL VESSELS vAoUUM Walter Diillenbach,Berlin-harlottenburg, Germany Application October 25, 1934, Serial No.749,984

In Germany October 30, 1933 7 Claims.

sleeve is sintered at high temperature, a vacuumtight connection iseffected between said sleeve and said plug, on the one hand, and betweensaid sleeve and the tank, on the other hand.

It is very difficult to obtain a reliable electrode lead-in for vacuumdischarge apparatus with metal tanks, particularly if such tanks aresubjected to treatment at 300 to 400 degrees for permanently separatingthem from the vacuum Various solutions of the problem have already beenproposed and are substantially satisfactory with regard to reliability.However, the existing lead-ins require extra supporting means for theelectrodes whose weight is considerable, particularly for heavycurrents. The vacuum-tight sealing means themselves cannot support theelectrodes, and it is obvious that the initial cost of the lead-in ismuch increased by the extra supporting means.

It has also been proposed to provide an insulating member of refractorymaterial which is connected to the vacuum tank and directly supports theweight .of the corresponding electrode. However, it has not beenpossible heretofore to effect a connection between the insulating memberand the electrode, and the wall of the tank.

which is permanently vacuum-tight and, at the same time, able to supportthe weight of the electrode, so that connections including an insulatingmember of the kind referred to, had to be abans doned notwithstandingtheir simplicity and cheapness.

Ihave found that the failure of the said leadins is due to the use ofunsuitable materials and unsuitable connecting means.

According to my invention, areliable and highly vacuum-tight lead-in isobtained by utilizing the sintering of the insulating member for makingthe connection between the electrode and the member on the one hand, andthe member and the wall of the tank, .on the other hand, or by obtainingthe connection through the medium initial product being normally talc.

of a glass or enamel melt whose heat-expansion coefficient issubstantially equal to that of the material of the insulating member.The areas of the faces by which the parts are connected, are made solarge that the mechanical stresses from the weight of the electrodes aretaken up without extra. supporting means for the electrodes.

Thorough investigation has demonstrated that in the manner described anelectrode lead-in is obtained in which the weight of the electrodes iswhose heat-expansion coeflicient is substantially equal to that of theinsulating member, and the melt. However, the heat-expansion coeflicientof the metalparts may be somewhat higher than that of the insulatingmember and the melt, as this brings about shrinking which is favorablefor the tightness and strength of the connection.

As the connection by sintering of the insulating member, or by glass orenamel melt, is made at very high temperatures, the electrode lead-in isabsolutely resistant to the aforesaid heating to 300 to 400 degrees forremoving the gas from the tank.

' In the accompanying drawing, three types of lead-ins embodying myinvention are illustrated by way of example.

In the drawing Fig. 1 is a section of a lead-in whose insulating memberis sealed against leakage by sintering of the member onto the metalparts, and

Fig. 2 is a section of a lead-in which is sealed by a melt. v

Referring now to the-drawing, and first to Fig. 1, the wall of a vacuumtank is indicated at I, and the conductor 4 of an electrode 5 is ledinthrough an insulating member or sleeve l. The sleeve is made ofrefractory material, preferably steatite, which, as is known, is arefractory prod uct' obtained by burning silicate of magnesia, theSteatite is superior to porcelain not only on account of its greatermechanical strength but also because it has a higher coeflicient of heatexpansion which is equal to glass or iron.

A- plug 2 of metal is inserted at the upper end of sleeve I and anannulus 3, also of meta? is placed'about the sleeve at its lower end.The plug 2 a nd the annulus 3 are made of a metal, or alloy, whoseheat-expansion coeflicient is substantially equal to that of therefractory 'mabe reduced to less than millionths per de- 5 gree byalloying with nickel, chromium, or vanadium. Two or more of the saidmetals may be added to iron for reducing its heat-expansion coemcient,and alloys of chromium and nickel may be used instead of iron alloys.Whatever may be the constituents of the alloy, they should be soselected as to make the heat-expansion coenlcient of the metal partssubstantially equal to that of the sleeve l.

The plug 2, and the annulus 3, are embedded in the sleeve I while thesleeve is in unburnt condition, and a vacuum-tight connection is thusobtained. Upon burning, the steatite and the metal parts are permanentlyand vacuumtightly connected by sintering. After the unit including thesleeve I, the plug 2, and the annulus I, has been burnt in a suitablefurnace, it is removed and the conductor 4 of the electrode I isinserted in a central hole of the plug. and welded. Preferably, anannular welding groove is formed in the boss of the plug at 8. A wiremay be connected to the conductor 4 by a bore I in its outer end.Finally, the annulus I is inserted in a hole of the wall I, and weldedto the wall.

The unit i, I, I is built up as a self-contained part because, asdescribed, it is burned in a furnace while the welding operations at 2and I can be performed anywhere, and because its metal parts 2 and I arecomparatively small and cheap in proportion, asagalnst a tank made ofchromium-nickel or other alloy, whose cost would be prohibitive.Referring now to Fig. 2, the arrangement of parts is the same asdescribed with reference 40 to Fig. 1 but here the plug 2 is'connectedto the sleeve l by a melt I of glass or enamel, and the annulus isconnected to the sleeve by a melt I. The operation is performed withoutdifficulty, as the melting point of the glass or ensmel is normallybelow the point at which the steatite of the sleeve becomes plastic. Theheat-expansion coemoient of the melt should besuhstantially equal tothat of the metal or alloy of the plug I and annulus I, and of the anyrmed by the movement of aline. around another line to which the firstline is 1 parallel, and therefore includes elements ofany 0 crosssection.

I claim:

1. A short, shallow seal for a lead-in construction for vacuum dischargeapparatus. comprising a metal member adapted to form a part 06 of thewall of a vacuum vessel, a metal electrode lead-in adapted to support anelectrode, an insulating member fitting in said metal member formporting directly said lead-in, said insulating member comprising asleeve of steatite, said 70 lead-in passing through. said sleeve, ametalplug secured'to said lead-in and secured'to said sleeve, the areas ofcontact between said sleeve and said metal member and plug having sub-.stantlally cylindroidal form, said metalmemllberandplusbein'gformedofmaterialhaving substantially the samecoefliclent of expansion as steatite, and sealing Joints at said areasof contact forming a vacuum tight seal between said sleeve and saidmetal member and plug, the axial lengths of said sealing joints beingrelatively short compared to the diameters thereof.

2. In a device as claimed in claim 1, said metal member and plug beingcomposed of an alloy selected from the group consisting of nickeliron,chromium-iron, vanadium-iron, and chromium-nickel alloys.

3. A short,shallow seal for a lead-in construction for vacuum dischargeapparatus, comprising a metal member adapted to form a part of the wallof a vacuum vessel, is metal electrode leadin adapted to support anelectrode, an insulating member fitting in said metal member forsupporting directly said lead-in, said insulating member comprising asleeve of steatite, said lead-in passing through said sleeve, a metalplug secured to said lead-in and secured to said sleeve,

the areas of contact between said sleeve and said metal member and plughaving substantially cylindroidal form, said metal member and plug beingiormed of material having substantially the same coefficient ofexpansion as steatite, and

contact forming a vacuum tight seal between said sleeve and said metalmember and plug,

sulating member fitting in said metal member for supporting directlysaid lead-in, said insulating member being formed of steatite, saidleadin passing through said insulating member, a-

metal plug secured to said lead-in and secured to said insulatingmember, the areas of contact between said insulating member and saidmetal member and plug having substantially cylindroidal form, wherebymechanical strains arising at the point of connection between theinsulating member and the metal parts are taken up without provision ofany othersupport for the electrode, said metal member and plug beingformed of material having substantially the same coemcient of expansionas steatite, and sealing Joints oi a fused material at said areas ofcontact forming a vacuum tight seal between said insulating member andsaid metal member and plug, the axial lengths of said sealing Jointsbeing relatively short compared to the diameters thereof.

5. A short, shallow seal for a lead-in construction for vacuum dischargeapparatus, comprising a metal member adapted to form a part of the wallof a vacuum vessel, a metal electrode lead-in adapted torsupport anelectrode, an insulating member fitting in said metal member forsupporting directly said lead-in, said insulating member being formed ofsteatite, said lead-in passing through said insulating member, a metalplug secured to said lead-in and secured to said insulatmember andplugbeing formed of material having member, the areas of contact betweensaid ining substantially the same coemcient of expansion assteatite, andsealing joints oi a fused material selected from the group consisting oiglass and enamel and having substantially the same coeiiicient ofexpansion as steatite at said areas of contact forming a vacuum tightseal between said insulating member and said'metal member and plug,th'e'axial lengths of said sealing joints being relatively shortcompared to the diameters thereof.

6. A short, shallow seal for a lead-in construetion for vacuum dischargeapparatus, comprising a metalmember adapted to form apart of the wall ofa vacuum vessel, a metal electrode leadin adapted to support anelectrode, an insulating member fitting in said metal member forsupporting directly said lead-in, said insulating member being formed ofsteatite,- said lead-in passing through said insulatingmember, a metalplug' secured to said lead-in and secured to said insulating member, theareas oi contact between having substantially the same coefllcient ofexpansion as steatite, and sealing joints termed by fusion of saidsteatite with said metalmemvacuum tight seal between said insulatingmember and said metal member and plug, the axial lengths of saidsealingjoints being relatively short compared to the diameters thereof.

7. In a device as claimed in claim 6, said metal member and plug beingcomposed of an alloy selected from the group consisting of nickel-iron,chromium-iron, vanadium-iron, and chromiumnickel alloys;

WAL'I'ER niimnmaacn,

10 ber and plug at said areas of contact forming a

